The mammalian pineal complex has been widely studied as an integral component of the neuroendocrine-reproductive axis. Although he rodent pineal is divided into superficial and deep components, only the superficial gland has been studied in detail. The deep pineal of rodents is in immediate contact with the third ventricle and has morphological features that indicate interaction with the cerebrospinal fluid (CSF). This proposal addresses the question of how the pineal gland interacts with the CSF in both the intact system and in pineal grafts placed into the third ventricle. Pineal grafts will also be used to study the effects of the pineal on LH, FSH, and prolactin secretion from the intact adenohypophysis as well as from the adenohypophysis when it is co-transplanted with pineal glands beneath the renal capsule or into the hamster cheek pouch. The specific aims of this proposal are to test the following hypotheses: (1) There are structural relationships within the pineal complex which form an anatomical basis to explain potentia interaction between CSF-contacting pinealocytes, non-CSF- contacting parenchymal cells of the deep pineal and cells of the superficial pineal, (2) Pinealocytes have the ability to take up substances in the CSF but only if they display the morphology of normal CSF-contacting pinealocytes; CSF-contacting pinealocytes in situ can transport substances from the CSF to the superficial pineal, indicating the existing of a pathway for the potential transport of substances between non-CSF-contacting pineal parenchymal cells and the CSF; (3) Superficial pineal grafts in the third ventricle will display normal pinealocyte morphology and secret melatonin but only if reinnervated by catecholaminergic neurons; such grafts will not display a circadian rhythm in melatonin secretion but they will decrease LH, FSH and prolactin secretion, suppress estrous cyclicity and result in testicular regression; and (4) The superficial pineal gland transplanted to the periphery will secrete melatonin which will stimulate prolactin but not LH and FSH secretion but only if reinnervated by catecholaminergic neurons. Techniques to be used include light and electron microscopy techniques including autoradiography (3H- melatonin) and immunohistochemistry (S-ag, LH, FSH, prolactin, tyrosine hydroxylase), 3-dimensional computer reconstruction of pinealocytes, morphometric analyses, and radioimmunoassays (LH, FSH and prolactin). The present proposal will contribute valuable information regarding CSF-pineal as well as pineal-adenohypophyseal interactions and their effects on the reproductive system.